Calculate Position of q2 When Speed is 8m/s Given Two Charges Energy

In summary: Ek = 1/2mv^2 V = qV2In summary, the charge q1 is at a position x2 when it reaches a speed of 8.00 m/s. a is the distance between q1 and q2.
  • #1
salman213
302
1
1. Two charges are arranged on the x axis. q1 = +8.00 μC, and
q2 = +5.00 μC. a = 25.0 cm. q1 is held fixed and q2 is released from rest.
Both q1 and q2 have a mass of 20.0 g.
Calculate x2, the position of q2, when it reaches a speed of 8.00 m/s.
a is the distance between q1 and q2. q1 is at the origin and q2 is along the x-axis at a distance "a"


2. Ek= 1/2mv^2
V = kq/r



3.
first i converted m to kg = 20 x 10^-3

Ek = 1/2mv^2
V = kq1/r + kq2/r

1/2mv^2 = kq1/r + kq2/r
1/2(20x10^-3)(8)^2 = k(8x10^-6)/x + k(5x10^-6)/(x-0.25)

solving for x gives me wrong answer
 
Physics news on Phys.org
  • #2
salman213 said:
Ek = 1/2mv^2
V = kq1/r + kq2/r

Why are you adding the potential energies? You are supposed to be equating the energy of the initial state (which is purely potential) to the energy of the final state (which is a combination of kinetic + potential).
 
  • #3
so initially

Ei = kq1/r2

and final

Ef = 1/2mv^2 + kq1/r

?
 
  • #4
salman213 said:
so initially

Ei = kq1/r2

and final

Ef = 1/2mv^2 + kq1/r

?

That sounds almost right. But also remember, voltage is not the energy of the charge. It is the energy a 1C of charge would have, but you do not have 1C charges now.
 
  • #5
but doesn't the forumula incorporate teh charge

kq/r
with that "q"
 
  • #6
salman213 said:
but doesn't the forumula incorporate teh charge

kq/r
with that "q"

Nope, the q1 is the voltage DUE TO the charge q1, not the energy OF q2. :)
 
  • #7
so does the answer of it involve the formula

W = q(vf-vi)

:S:S:S
 
  • #8
salman213 said:
so does the answer of it involve the formula

W = q(vf-vi)

:S:S:S

Yes, the energy of the charge is given by qV, where V is the voltage at a point.
 
  • #9
ok but how would i incorporate the energy due to charge 1 that is held fixed..

so far Ek = 1/2m1v1^2
V = qV2

is that all i need or in Ek I need to add the potential of the fixed charge
 
  • #10
kq1q2/.25 = 1/2mv^2 + kq1q2/(x-0.25)
 

1. How do you calculate the position of q2?

To calculate the position of q2 in this scenario, you will need to use the Coulomb's law formula: F = k(q1q2)/r^2, where k is the Coulomb's constant, q1 and q2 are the two charges, and r is the distance between them. With this formula, you can find the electric force between the two charges and use it to determine the position of q2.

2. What is the speed of q2?

The speed of q2 is given as 8m/s in this scenario. This means that q2 is moving at a constant rate of 8 meters per second.

3. What are the units for the charges and speed?

The charges are measured in Coulombs (C) and the speed is measured in meters per second (m/s).

4. Can you calculate the position of q2 with only the speed and charges given?

No, in order to calculate the position of q2, you also need to know the distance between the two charges. Without the distance, you cannot use the Coulomb's law formula to determine the position.

5. How does the energy of the charges affect the position of q2?

The energy of the charges does not directly affect the position of q2. However, the energy can influence the distance between the charges, which in turn can affect the position of q2. This is because the electric force between the charges is inversely proportional to the square of the distance between them, so a change in energy can lead to a change in distance and thus a change in position.

Similar threads

  • Introductory Physics Homework Help
Replies
10
Views
1K
  • Introductory Physics Homework Help
Replies
2
Views
1K
  • Introductory Physics Homework Help
Replies
9
Views
3K
  • Introductory Physics Homework Help
Replies
2
Views
1K
  • Introductory Physics Homework Help
Replies
18
Views
3K
  • Introductory Physics Homework Help
Replies
3
Views
1K
  • Introductory Physics Homework Help
Replies
1
Views
2K
  • Introductory Physics Homework Help
Replies
3
Views
3K
  • Introductory Physics Homework Help
Replies
3
Views
3K
  • Introductory Physics Homework Help
Replies
16
Views
2K
Back
Top